Re: Is there a way to force legacy LE pairing for a device

[Jacek Konieczny <jajcus@jajcus.net>]

Hi Marcel,

On 11/2/21 9:43 AM, Marcel Holtmann wrote:
> you can use btmgmt tool from bluez.git to force Secure Connections off. I am not sure if that sticks when starting bluetoothd, but then you need to hack it out there.

Thank you! This works. I had to run 'btmgmt sc off' after starting
bluetoothd, before 'power on', but then I was able to pair with my
device. When paired MIDI over Bluetooth is working properly.

Even after I re-enable SC the connection with the already-paired device
works.

I think I can work with that.

> I am really not sure how your device can be a qualified Bluetooth device and fail here. The handling of the flags has actually proper test cases to ensure that this does’t happen.

That would not be a first time when a device is compatible with the
standard it is advertised with. Especially that for this one this is
extra feature hardly anyone uses and the manufacturer does not even
support their own software properly (the Android app just doesn't work)
and usually the USB interface would be rather used than BT, anyway.

What is interesting this amplifier has two different BT adapters. It can
function as a 'bluetooth speaker' and this seems to be working without
any issue. It is the 'regular Bluetooth', not LE. This one feature would
be probably enough to call this Bluetooth device.

The other function is amplifier remote control via MIDI over Bluetooth.
This seems to be a separate BLE interface and works as I described. It
does not even have any special 'pairing mode' (the 'speaker' function
requires pressing a button on the device) or pairing verification, so
anyone can pair with the amplifier at any time (unless already someone
else uses the BLE interface) and change its settings. It would be quite
an interesting attack if anyone used those devices on stage. Using SC or
not probably does not matter at this point at all.

Greets,
Jacek